62 



Appendices to Fourth Annual Report 



As the plan which I have adopted for carrying out a similar investi- 

 gation into the herring of the Scottish coasts differs in some of its details 

 from Dr Heinckc's, it must be explained that I had not read his paper 

 until my own observations were almost completed, otherwise I would have 

 taken measures for more readily comparing my results with his in detail, 

 although I still prefer my own method as being in some slight respects 

 more exact. The amount of labour involved in revising the work in detail 

 for this purpose is, however, so great, that meantime it must be delayed, 

 and where I have been able to make comparisons, it has mostly been with 

 the concluding summary in Dr Heincke's paper.* The experience gained 

 in measuring the first few fish received for the purpose of the investi- 

 gation, was sufiicient to show that a general preliminary examination of the 

 results likely to be procured was necessary, in order to ascertain the best 

 way in which these could be obtained. As the result of such an exami- 

 nation, it was early found that fish of the same length, and as nearly as 

 possible of the same bulk, differed as to their dorsal and anal fins, not 

 only in the position of these relatively to the length of body, but that the 

 fins themselves varied both as to the length of their bases, and also in 

 respect to the relative length of the individual rays, measured from their 

 bases to their tips ; a circumstance due not only to the different amount 

 of wear they had undergone, which is probably slight, but also to absolute 

 difference in the amount of their development, increased, as it likely is, 

 by the difference in age of the fish. This led to an examination of the tail 

 to ascertain whether the caudal fin was subject to similar variations, which 

 might reduce the value of the total length of the fish as a basis for com- 

 parison of the other characteristics. In several cases it was clear that the 

 length of the caudal fin was affected by wear, or by injury received after 

 the capture of the herring. But a far greater difference was found in the 

 actual length of the caudal fin rays as measured from their proximal ends, 

 and also from the termination of the intervening and supporting hypural 

 bones, in herrings as nearly alike as possible in the length and bulk of their 

 bodies. 



It was evident also that the fish (which were in all cases perfectly fresh 

 when measured), were subject to very considerable variation in the position 

 of the lobes of the caudal fin, caused apparently by the amount of mus- 

 cular contraction after death, and, as a consequence of this, there of course 

 resulted a considerable degree of variation in the total length of the fish 

 (sometimes as much as 10 mm.), according to whether the lobes were 

 approximated so as to be in nearly a straight line behind the body, or 

 were widely spread. 



For the purpose of comparison by measurement of those characteristics 

 which were suited for being thus dealt with, any standard would be suit- 

 able, so long as it was not itself liable to much variation ; and I resolved, 

 therefore, to dispense with the employment of the total length including 

 the caudal fin, as a basis, as being too likely, from the variation in length 

 of the fin, to detract from the value of the results. Note was, however, 

 taken of the length of the caudal fin, with the view of testing its 

 variability correctly. The result was, that the length from tip of closed 

 lower jaw to a point near base of caudal fin was fixed on as the most 

 reliable, all that was necessary being that that point should be an easily 

 ascertainable position. Probably the termination of the vertebral column 

 would be the best ' total length,' but the additional work involved in ex- 



* The amount of almost ' drudgery ' entailed in an investigation of this nature is 

 scarcely realisable by those who have not undertaken it. In my own case the 

 mechanical work entailed amounted to the taking of about 16,000 measurements on 

 the herrings, with over 20,000 subsequent calculations. 



